PURPOSE: Lymphatic drainage from renal tumors is unpredictable and in vivo drainage studies of primary lymphatic landing sites may reveal the variability and dynamics of lymphatic connections. The purpose of this study was to investigate the lymphatic drainage pattern from renal tumors in vivo with SPECT/CT imaging after intra-tumoral radiotracer injection.
MATERIALS AND METHODS: We conducted a phase II prospective single-arm study to investigate the distribution of SNs from renal tumors on SPECT/CT imaging. Patients with cT1-3 (<10 cm) cN0M0 renal tumors of any subtype were enrolled. After intra-tumoral ultrasound guided injection of 0.4 ml99mTc-nanocolloid, preoperative imaging of SNs with lymphoscintigraphy and SPECT/CT was performed. SN and locoregional non-SNs were resected using a gamma probe in combination with a mobile gamma camera. The primary study endpoint was location of SNs outside the locoregional retroperitoneal templates (LRT) on SPECT/CT imaging. Using a Simon Minimax two-stage design to detect a 25% extra-LRT location of SNs on imaging with an alpha of 0.05 and a power of 80%, at least 40 patients with SN imaging on SPECT/CT were needed.
RESULTS: Sixty-eight patients were included. Forty patients had preoperative SPECT/CT imaging of SNs and were used for primary endpoint analysis. Lymphatic drainage outside the LRT was observed in 14 (35%) patients. Eight patients (20%) had supradiaphragmatic SN.
CONCLUSIONS: SNs from renal tumors were mainly located in their respective LRT, but simultaneous SNs located outside the suggested LND templates, including supradiaphragmatic SNs were observed in more than one third of the patients.